The relation between changes in myocyte orientation and contractile function with electrical field stimulation.
The cardiac myocyte is the fundamental contractile unit of the heart, and therefore recent studies have examined myocyte function through electrical field stimulation. However, the relation between changes in electrical field orientation and myocyte contractile function remains unclear. Accordingly, the goal of the present study was to measure myocyte contractile function with known changes in myocyte orientation with respect to the electrodes. Isolated left ventricular porcine myocytes (n = 32) were field stimulated (0.5 - 1.5 Hz, 5 ms, double contraction threshold) in a thermostatically controlled chamber. Myocyte velocity of shortening was measured by high speed video microscopy. Myocyte position was altered and quantified with respect to the electrodes. When myocyte position approached alignment with the electrodes, contractile activity ceased. Contractile activity resumed when the myocyte moved greater than 25 degrees from the parallel position. When contractions could be successfully elicited, the velocity of shortening was 48+/-15 microm/s and did not differ at any orientation. These results suggest that angular orientation should be carefully considered when evaluating the contractile performance of electrically stimulated myocytes.
Hedgepath
K R
KR
Cardiothoracic Surgery, Medical University of South Carolina, Charleston 29425, USA.
Mukherjee
R
R
Wang
Z
Z
Spinale
F G
FG
D000818:Animals; D016764:Cell Polarity / Q000502:physiology; D002469:Cell Separation; D048429:Cell Size / Q000502:physiology; D002478:Cells, Cultured; D016001:Confidence Intervals; D004558:Electric Stimulation; D004566:Electrodes; D009119:Muscle Contraction / Q000502:physiology*; D009206:Myocardium / Q000166:cytology*; D013552:Swine